The present invention relates to an attachment for holding a thread cutting tool in a turning machine such as a lathe, and constitutes an improvement over prior art attachments such as shown in my U.S. Pat. No. 3,011,185 issued Dec. 5, 1961, U.S. Pat. No. 3,179,965 issued Apr. 27, 1965 and U.S. Pat. No. 3,821,826 issued July 2, 1974.
In my U.S. Pat. No. 3,821,826, an attachment is disclosed in which a tap is fixedly connected to a carrier slidably mounted on a stationary spindle in a turning machine. A releasable torque transmitting connection is formed between the spindle and carrier and automatically uncouples the tool and spindle and thus terminates a thread cutting operation after the tool has advanced a predetermined amount into or through the workpiece. If, however, it is desired to cut threads in a blind pilot hole, then special set up and starting operations must be followed otherwise the tap reaches the bottom of the blind hole and attempts to continue advancing into the hole with resulting damage to either the workpiece, the tool, the attachment or the turning machine.
It is, accordingly, a general object of the present invention to provide an improved threading attachment for a turning machine which permits the tapping of either through-holes or blind holes without damaging the thread cutting equipment and also without special set up procedures beforehand.